ABSTRACT

The basic full-wave uncontrolled (diode) rectifier circuit is shown in Fig. 6.1. Diodes D1, D3, and D5 are sometimes referred to as the upper half of the bridge, while diodes D2, D4, and D6 constitute the lower half of the bridge. As with half-wave operation the voltages at the anodes of the diode valves vary periodically as the supply voltages undergo cyclic excursions. Commutation or switch-off of a conducting diode is therefore accomplished by natural cycling of the supply voltages and is known as natural commutation. The load current iL is unidirectional, but the supply currents are now bidirectional. In order to permit load current to flow, at least one diode must conduct in each half of the bridge. When this happens, the appropriate line-to-line supply point voltage is applied across the load. In comparison with the half-wave bridge (Fig. 4.2a), in which the supply-phase voltage is applied across the load, the full-wave bridge has the immediate advantage that the peak load voltage is times as great.